It is conventionally known that nanometer-sized particles (nanoparticles) are used in optical materials.
For example, a method has been proposed in which organomodified fine particles are obtained by subjecting fine particles of a metal oxide such as SiO2 or TiO2 and an organic modifier to a hydrothermal synthesis (see, for example, Patent Document 1 listed below).
Also, it is long known that oxides such as titanium oxide exert a photocatalytic action.
For example, it is known that oxides such as titanium oxide, strontium titanate and tungsten oxide decompose organic substances by their photocatalytic action (see, for example, Non-Patent Document 1 listed below).
It is also long known that porous resin obtained by porosifying resin exhibits various physical properties due to porosification, in addition to the physical properties inherent to resin.
For example, a method has been proposed in which porous polyimide resin is obtained by blending polyethylene glycol dimethyl ether with a polyimide resin precursor so as to prepare a mixed resin solution, forming a coating and then bringing the coating into contact with hot high pressure carbon dioxide so as to extract polyethylene glycol dimethyl ether (see, for example, Patent Document 2 listed below).
The porous polyimide resin disclosed in Patent Document 2 has uniformly formed pores (cells), and the dielectric constant of the porous polyimide resin is set lower than that of non-porous polyimide resin.
It is also long known that titanium oxide particles for use in various industrial products are prepared in organic solvents or the like. Meanwhile, from a view point of reducing the environmental load in recent years, various methods are being studied to prepare titanium oxide particles in water, which imposes little load to the environment as compared to organic solvents or the like.
To produce such titanium oxide, for example, a titanium oxide particle producing method has been proposed in which titanium oxide particles are prepared by treating a titanium complex containing glycolic acid as a ligand in hot high pressure water (see, for example, Non-Patent Document 2 listed below).